Formation of Low-Dimensional Double Perovskite Layers by ABS and PEAI Sequential Treatment for Achieving High-Performance CsPbI3 Solar Cells

All-inorganic CsPbI 3 perovskite has emerged as an alternative photovoltaic material owing to its good thermal stability and ideal bandgap for tandem applications. However, CsPbI 3 perovskite solar cells (PSCs) still show poor phase stability and low efficiency. Herein, we propose a new strategy to form low-dimensional double perovskite (2D-PEA 2 PbI 4 and quasi-2D-PEA 2 (CsPbI 3 )PbI 4 ) layers on the CsPbI 3 film by sequential treatment with ammonium benzenesulfonate (ABS) and phenylethylammonium iodide (PEAI). After ABS treatment, additional PbI 2 was in situ formed on the CsPbI 3 film surface, which further reacted with PEAI to generate low-dimensional double perovskite layers. The low-dimensional double perovskite layers effectively enhanced the efficiency and stability of CsPbI 3 solar cells. Consequently, a power conversion efficiency (PCE) of 19.06% is achieved. The unencapsulated device retained approximately 70% of its initial PCE after aging 300 h under ambient conditions. This study provides a new approach for the application of low-dimensional perovskites in all-inorganic PSCs.